The present invention relates to functional electrical stimulation (FES) devices and systems and, more particularly, to an improved envelope for force-sensitive resistors of such devices, and to FES devices and systems having improved monitoring, analysis, control, safety, energy conservation, and communication features.
It is known that various pathologies of the neuromuscular system due to disease or trauma to the central nervous system, such as stroke, spinal cord injury, head injury, cerebral palsy and multiple sclerosis, can impede proper limb functioning of the legs. Gait, the biomechanical description of walking, can suffer static and dynamic parameter variations due to neuromuscular impairments that cause non-symmetrical walking and reduced walking speed and stability, and often require increased energy consumption.
Drop foot describes the gait attributable to weak or uncoordinated activation of the ankle dorsi-flexors due to disease or trauma to the central nervous system. A patient suffering from drop foot tends to drag the foot during the swing phase of walking and usually try to compensate for this dragging by hiking the hip or swinging the affected leg in a circular motion. These patients tend to have impaired stability, are prone to frequent falls, and have walking movements that are unaesthetic and energy consuming.
It is known, however, that functional electrical stimulation (FES) can generally be used to activate the leg muscles of such patients. Precisely timed bursts of short electrical pulses are applied to motor nerves to generate muscle contractions, which are synchronized with the gait of the patient, so as to improve the leg function and enhance the gait. The timing of these pulses is critical, and must be synchronized with the gait. This is advantageously achieved by sensing gait events such as a foot-floor force reaction, using a force-sensitive resistor (FSR) disposed beneath the heel region of the patient, and transmitting the information to the stimulator unit.
The FSR sensor must be protected against water, humidity, dirt, and mechanical stress by means of a casing or envelope.
U.S. Pat. No. 6,507,757 to Swain, et al., discloses one typical foot sensor device of the prior art, in which a foot pressure switch, or sensor, is permanently disposed in the shoe of the affected leg. An electrical circuit is interrupted during the stance phase, when a significant weight is placed on the heel, and reconnects when the heel is lifted during the swing phase. Wires disposed under the clothing connect the sensor with an external stimulator unit that can be attached to the belt or kept in a pocket of the user. The stimulator unit is connected to the electrodes by additional electrical wires.
The cumbersome wires may be obviated by using a radio frequency (RF) system in which the foot sensor device and other components of the FES orthotic system communicate in a wireless fashion. However, the use of such an RF system necessitates integrating an RF transmitting unit, or head, within the foot sensor device. The RF communication with other components of the FES orthotic system must be robust and reliable, even in areas in which various types of wireless signals are prevalent, such as local area networks (LANs). The FES orthotic system must also be robust and reliable in areas in FES clinics and the like, in which one or more additional wireless FES systems may be operating simultaneously.
There is therefore a recognized need for, and it would be highly advantageous to have, an FES orthotic system for neuroprosthetic gait enhancement that overcomes the various deficiencies of the known systems. It would be of particular advantage for such a system that is robust and reliable, avoids the discomfort associated with various prior art stimulation devices, and is secured so as to operate in a safe and robust fashion.